The characteristics and causes of the persistent precipitation of an extreme-rainfall tropical cyclone (TC), In-Fa, in 2021 are studied. It is shown that the extremity of In-Fa’s precipitation was mainly due to two aspects: massively accumulated quantity and an extremely long impact time. The heavy precipitation in Zhejiang resulted from the accumulation of very long but moderate precipitation, while that in Jiangsu resulted from the coaction of both long duration and strong intensity. The weak steering flow brought about by the large scale environment and the long continuation of the TC’s circulation were the two most important background conditions for the extremely long duration of heavy rainfall in Zhejiang and Jiangsu. Continuous energy input through the transportation of warmer and wetter air resulted in the persistence of In-Fa’s circulation. The terrain effect under the continuous northeasterly/northerly airflow caused by the slow movement of the TC was the major influencing factor for the extreme precipitation in Zhejiang. The convergence brought about by the TC’s vortex during landfall played another role in Zhejiang’s heavy rainfall. On the one hand, the terrain led to the development of low-level vertical circulation, resulting in convergence and updraft in the windward side of Siming Mountain; on the other hand, the terrain also provided for the vertical transport of water vapor. The main factors for the extreme precipitation in Jiangsu were the long continuation of low-level jets that caused persistent low-level convergence and the development of a mesoscale rainband. The convergence zone was located in the western front and evolved with the changing of the jets. The high-energy/high-humidity conditions and their consistency with the location of the convergence provided favorable conditions for the triggering and development of convection.

In this study, the impact of surface water body on the evolution of thunderstorm events crossing Hangzhou Bay is investigated based on the observations and numerical simulations. The organized convective systems crossing Hangzhou Bay usually weaken first after moving onto the water surface, and then re-intensify after landing onto southern coastline. The weakening of storm over the bay is mainly ascribed to the low water surface temperature, that is, the decreasing of water surface temperature is unfavorable for the development of storm. The re-intensification of storm over the southern coastline is due to the boundary layer convergence strengthening along the sea–land interface. For the organized thunderstorm, the enhancement of large-scale onshore wind can increase boundary layer convergence along both northern and southern coastlines, which leads to enhancement of convection and precipitations on the northern coastline.

Using multi-source global station and grid monitoring data, FY-2H satellite, and ERA5 reanalysis data, the life history and precipitation characteristics of tropical cyclone "Freddy" as well as the causes of heavy precipitation in southern Mozambique were analyzed. The results show that "Freddy" had a lifespan of 35.5 days which made it the longest lived tropical cyclone in the world, as well as the widest latitude-crossing TC in the southern hemisphere. The extreme long life cycle of "Freddy" was related to favorable large-scale circulation conditions. The strong and sustained subtropical high pressure system made "Freddy" moving westward over the Southern Indian Ocean stably, without the opportunity to combine with the mid latitude trough or cold air which may cause the path turning, intensity weakening, or transformation. After the generation of "Freddy", more than 70% of its life time was over the sea, and the surrounding SST was generally abnormally high, which provided favorable conditions for the development or maintenance of TC intensity. Especially, the SST within the Mozambique Strait remained above 28 ℃, providing excellent underlying conditions for the enhancement of TC intensity, allowing "Freddy" to develop and strengthen rapidly twice after experiencing intensity weakening caused by landfall. The combined influence of favorable circulation conditions and warm sea surface temperature led to the extreme long life of "Freddy". "Freddy" made three landfall, bringing sustained heavy precipitation and severe floods to countries in Southeastern Africa. Especially in the southern part of Mozambique, precipitation had characteristics such as long duration, concentrated areas, and large accumulated amount. After landing in Mozambique, "Freddy" was located in a saddle field, leading to weakened steering airflow. Combined with high-level divergence and sustained transportation of warm and humid air by low-level jet, the large-scale circulation system provided favorable background conditions for the slow movement and maintenance of tropical cyclone. The development of low-level convergence and vorticity bands in lower troposphere, as well as strong and sustained water vapor transport, led to the persistence of heavy rainfall in Mozambique. The invasion of cold air induced the formation of a pseudo equivalent potential temperature high-gradient zone in southern Mozambique, and the cold air in the middle layer enhanced atmospheric instability, which was conducive to the development of convection. The southern part of Mozambique was continuously affected by several mesoscale convective systems (MCSs), which not only improved precipitation efficiency but also prolonged the duration of precipitation. The evolution of MCSs had obvious diurnal variation characteristics, with its rapid development and maturity stages almost concentrating in the afternoon to the earlier evening of local time. The increase in low-level wind speed promoted the enhancement of both water vapor and energy, and under the above conditions, the convergence of tropical cyclone wind direction and wind speed triggered the generation of MCSs continuously.

Using multi-source global station and grid monitoring data, FY-2H satellite, and ERA5 reanalysis data, the life history and precipitation characteristics of tropical cyclone "Freddy" as well as the causes of heavy precipitation in southern Mozambique were analyzed. The results show that "Freddy" had a lifespan of 35 days which made it the longest lived tropical cyclone in the world, as well as the widest latitude-crossing TC in the southern hemisphere. The extreme long life cycle of "Freddy" was related to favorable large-scale circulation conditions. The strong and sustained subtropical high pressure system made "Freddy" moving westward over the Southern Indian Ocean stably, without the opportunity to combine with the mid latitude trough or cold air which may cause the path turning, intensity weakening, or transformation. After the generation of "Freddy", more than 70% of its life time was over the sea, and the surrounding SST was generally abnormally high, which provided favorable conditions for the development or maintenance of TC intensity. Especially, the SST within the Mozambique Strait remained above 28 ℃, providing excellent underlying conditions for the enhancement of TC intensity, allowing "Freddy" to develop and strengthen rapidly twice after experiencing intensity weakening caused by landfall. The combined influence of favorable circulation conditions and warm sea surface temperature led to the extreme long life of "Freddy"."Freddy" made three landfall, bringing sustained heavy precipitation and severe floods to countries in Southeastern Africa. Especially in the southern part of Mozambique, precipitation had characteristics such as long duration, concentrated areas, and large accumulated amount. After landing in Mozambique, "Freddy" was located in a saddle field, leading to weakened steering airflow. Combined with high-level divergence and sustained transportation of warm and humid air by low-level jet, the large-scale circulation system provided favorable background conditions for the slow movement and maintenance of tropical cyclone. The development of low-level convergence and vorticity bands in lower troposphere, as well as strong and sustained water vapor transport, led to the persistence of heavy rainfall in Mozambique. The invasion of cold air induced the formation of a pseudo equivalent potential temperature high-gradient zone in southern Mozambique, and the cold air in the middle layer enhanced atmospheric instability, which was conducive to the development of convection. The southern part of Mozambique was continuously affected by several mesoscale convective systems (MCSs), which not only improved precipitation efficiency but also prolonged the duration of precipitation. The evolution of MCSs had obvious diurnal variation characteristics, with its rapid development and maturity stages almost concentrating in the afternoon to the earlier evening of local time. The increase in low-level wind speed promoted the enhancement of both water vapor and energy, and under the above conditions, the convergence of tropical cyclone wind direction and wind speed triggered the generation of MCSs continuously.

In response to the critical global challenge of bridging the early warning capability gap—particularly for developing and least developed countries—this paper presents the Cloud-based Global Meteorological Early Warning Support Platform (C-EWS) developed by China Meteorological Administration (CMA). C-EWS embodies a novel operational paradigm designed to overcome the persistent scientific and logistical barriers that hinder effective early warning operations in resource-constrained settings.C-EWS integrates a lightweight, cloud-based architecture to ensure universal accessibility. Through server-side rendering, asynchronous data streaming, and a unified API gateway, the platform shifts computational burden to the cloud, enabling smooth interactive exploration of multi-gigabyte datasets even over low-bandwidth connections. The platform consolidates multi-source observational data (including Fengyun satellite and WMO GTS observations), global NWP models (CMA-GFS, ECMWF-IFS, NCEP-GFS, ICON, JMA-GSM), and AI forecasts ('Fengqing', ECMWF-AIFS) into a unified, interactive web environment.Unlike existing international platforms that offer either single-model expert products or basic multi-model visualization, C-EWS uniquely enables comprehensive multi-model diagnostic analysis, integrating both physics-based and AI-driven forecasts for enhanced uncertainty assessment. The platform embeds over 20 interactive analytical tools for multi-model comparison, forecast stability evaluation, and vertical profiling, enabling forecasters to rapidly analyze three-dimensional circulation patterns and assess model biases.C-EWS delivers a suite of multi-model-based objective early warning products covering multiple hazard types—including tropical cyclones, sand and dust storms, extreme heat, heavy precipitation, gale winds, and floods. Verification against 2025 forecast products demonstrates substantial skill improvements: for heavy rainfall warnings, TS reached 0.226–0.158 for short-range forecasts—improvements of over 26% compared to NWP model forecasts. Operational efficiency has also been significantly enhanced: the time required to produce comprehensive Global Hazardous Weather Bulletins has been reduced from approximately 3.5 hours to 1 hour (a 71% improvement), while the volume of early warning products issued has increased by 136%. The platform also employ a co-development framework, enabling partner countries to co-create tailored solutions.Since its operational deployment, C-EWS has supported forecasting for over 50 severe weather events across more than 30 countries and regions. Feedback from stakeholders confirms its practical value. The platform also supports multilateral mechanisms including WMO's Multi-Model Integrated Forecasting and Application (MMIFA) pilot project, the WMO Coordination Mechanism's (WCM) Hydrometeorological Weekly Scan, and the South Asia Hydromet Forum (SAHF) forecast consultations.This work establishes a scalable and scientifically robust pathway to broaden access to advanced forecasting capabilities for developing nations, directly contributing to the United Nations' "Early Warnings for All" (EW4ALL) initiative and strengthening global climate resilience. Future developments will focus on expanding data source integration, operationalizing hybrid NWP+AI approaches for sub-seasonal to seasonal forecasting, and developing self-service configuration tools for more scalable customization.